Our recent studies have shown that fasting augments growth hormone secretion. We hypothesize that there is a feedback loop between the metabolic milieu and hypothalamic-somatotroph axis. These studies will investigate the effect of metabolic hormones (e.g., insulin, glucagon) and intermediary metabolites (e.g., glucose, ketones, free fatty acids) on growth hormone secretion dispersed rat anterior pituitary cells in primary culture and on perifusion columns. These in vitro studies will complement our clinical trials.